1. Field of the Invention
This invention relates to a process for producing silica and to a rod-shaped silica formed thereby, and more particularly it relates to a process for producing a rod-form silica having a high aspect ratio.
2. Description of the Related Art
As a filler for a resin sealant for semiconductors, a crushed product of natural silica has been known. However, such a crushed silica has various problems such that it may cut the lead wire for semiconductors, when it is filled in the semiconductor, an erroneous operation may occur due to its insufficient purity, etc. In order to overcome such problems, there has been proposed a silica prepared according to a sol-gel process of adding water to a silicic acid ester to prepare a sol, followed by hydrolysis and dehydration-condensation reaction to prepare a wet gel. A silica gel is obtained by drying the wet gel, followed by sintering by heating to prepare silica. Further, a process of dispersing the sol in an organic solvent to obtain a silica in the same manner as the above (Japanese patent application laid-open No. Sho 58-176136/1983), and a process of further using a surfactant (Japanese patent application laid-open No. Sho 63-85012/1988) are disclosed.
Since the silica prepared according to a conventional sol-gel process is spherical, it is insufficient in mechanical strength for a filler of a resin sealant. Therefore, a rod-form silica having a high aspect ratio, which is expected to have a high mechanical strength in a resin sealant, has been desired.